"Hate to say I told you so" is how the phrase (and song!) goes, but more often than not, the smug sense of satisfaction when proven right is schadenfreude at its best.
A Reddit thread asked "What’s your 'I told you so' moment?" and people delivered with stories of times others didn't heed to their warnings when they really, really should have.
They were warned. They were given an explanation. Nevertheless, they persisted.
'1. From ool9i:
Working in a horse breeding barn - told a new employee that she might want to wear gloves when cleaning horse "sheaths." She said it wasn't necessary. Next day, she's complaining that even 10 washes wouldn't get the stench off her hands. The mares liked her, though.
2. From CayonSalad:
Since I was 14, my throat got itchy when I ate apples. I told my mom but she thought I just didn't want to eat apples and forced me to eat them. Went to the doctor's office and got a test for allergies. Turns out, I'm allergic to apples, peaches, and many other fruits.